Speciation processes in Eastern Mediterranean Orchis s.l. species: Molecular evidence and the role of pollination biology

Abstract

A molecular phylogenetic investigation, based on the internal transcribed spacers (ITS) of nuclear ribosomal DNA, was undertaken on members of Anacamptis, Orchis, Neotinea, and allied genera, focussing on taxa growing in the Near East and Eastern Europe, and especially in Israel. We found that Eastern Mediterranean orchids do not represent a monophylum, as they belong to all of the three genera into which Orchis s.l. has recently been divided. Although no general geographic distribution pattern may be inferred, some sister terminals either show a broad East/West distribution pattern across the Mediterranean or represent peripheral isolates from a more extended range. The evolution of some sibling species pairs seems to be related to the evolution of different pollination strategies. Anacamptis israelitica represents one of the rare cases of the existence of floral Batesian mimicry, while the endemic Orchis galilaea is the only species among the investigated taxa to be pollinated by sexual deceit, a strategy also implemented in the distant genus Ophrys. Differences in spur features occur between the Eastern Mediterranean Orchis anatolica and Anacamptis dinsmorei and their Western Mediterranean sister species; Anacamptis caspia closely resembles the eroica morphotype of the widespread Anacamptis papilionacea. These patterns of relationships suggest that differences in pollination strategies or in pollinator communities among geographically distant populations or other ecological conditions may lead to changes in floral morphology and biology and eventually to speciation.